Electrophysiologic evaluation before and after the serial administration of verapamil, lidocaine, propranolol, and procainamide was undertaken in 4 young, asymptomatic patients with recurrent, sustained ventricular tachycardia (VT). No patient had obvious organic heart disease. The electrocardiogram during sinus rhythm showed S-T depression and T-wave inversion over the inferior and lateral precordial leads in 3 patients. QRS morphologic characteristics during episodes of VT showed a pattern of right bundle branch block and left axis deviation. In all 4 patients, VT could be both induced and terminated with electrical stimulation. Verapamil terminated VT and prevented the induction of sustained VT in 3 patients, and markedly slowed the rate of VT in 1 patient. Procainamide effectively prevented the induction of sustained VT in 2 patients, and although ineffective in preventing induction in 2 patients, it slowed the rate of tachycardia in both. Lidocaine and propranolol did not prevent the induction of VT in any patient. These findings suggest that slow-response tissues may be involved in the genesis of VT in these patients, and that VT in these patients may represent a unique clinical entity with distinct electrocardiographic, electrophysiologic, and electropharmacologic properties.